Membrane estrogen receptor-alpha interacts with metabotropic glutamate receptor type 1a to mobilize intracellular calcium in hypothalamic astrocytes.
Estradiol, acting on a membrane-associated estrogen receptor-alpha (mERalpha), induces an increase in free cytoplasmic calcium concentration ([Ca(2+)](i)) needed for progesterone synthesis in hypothalamic astrocytes. To determine whether rapid estradiol signaling involves an interaction of mERalpha with metabotropic glutamate receptor type 1a (mGluR1a), changes in [Ca(2+)](i) were monitored with the calcium indicator, Fluo-4 AM, in primary cultures of female postpubertal hypothalamic astrocytes. 17beta-Estradiol over a range of 1 nm to 100 nm induced a maximal increase in [Ca(2+)](i) flux measured as a change in relative fluorescence [DeltaF Ca(2+) = 615 +/- 36 to 641 +/- 47 relative fluorescent units (RFU)], whereas 0.1 nm of estradiol stimulated a moderate [Ca(2+)](i) increase (275 +/- 16 RFU). The rapid estradiol-induced [Ca(2+)](i) flux was blocked with 1 microm of the estrogen receptor antagonist ICI 182,780 (635 +/- 24 vs. 102 +/- 11 RFU, P < 0.001) and 20 nmof the mGluR1a antagonist LY 367385 (617 +/- 35 vs. 133 +/- 20 RFU, P < 0.001). Whereas the mGluR1a receptor agonist (RS)-3,5-dihydroxyphenyl-glycine (50 microm) also stimulated a robust [Ca(2+)](i) flux (626 +/- 23 RFU), combined treatment of estradiol (1 nm) plus (RS)-3,5-dihydroxyphenyl-glycine (50 microm) augmented the [Ca(2+)](i) response (762 +/- 17 RFU) compared with either compound alone (P < 0.001). Coimmunoprecipitation demonstrated a direct physical interaction between mERalpha and mGluR1a in the plasma membrane of hypothalamic astrocytes. These results indicate that mERalpha acts through mGluR1a, and mGluR1a activation facilitates the estradiol response, suggesting that neural activity can modify estradiol-induced membrane signaling in astrocytes.
Kuo
John
J
Department of Neurobiology, David Geffen School of Medicine at University of California, Los Angeles, 10833 LeConte Avenue, 73-078 CHS, Los Angeles, California 90095-1763. pmicevych@mednet.ucla.edu.
Hariri
Omid R
OR
Bondar
Galyna
G
Ogi
Julie
J
Micevych
Paul
P
D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D004958:Estradiol / Q000494:pharmacology; D047628:Estrogen Receptor alpha / Q000378:metabolism*; D005260:Female; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism*; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D011485:Protein Binding; D051381:Rats; D020318:Rats, Long-Evans; D018094:Receptors, Metabotropic Glutamate / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects
D047628:Estrogen Receptor alpha; D018094:Receptors, Metabotropic Glutamate; C104077:metabotropic glutamate receptor type 1; D004958:Estradiol; D002118:Calcium